1. Field of the Invention
This invention relates to high temperature co-fired ceramic integrated phased array packaging incorporating microwave circuitry, electronic circuitry, antenna or radiating element and transitions in a single package.
2. Brief Description of the Prior Art
High frequency microwave multichip packages have been produced in the prior with machined metal housings, generally of aluminum or kovar, with feed-throughs to introduce RF into or withdraw RF from the package. These prior art packages are multiple material systems fabricated using many different processing steps which are very costly since the packages cannot be fabricated in a fully automated operation in large quantity by such processing techniques.
Low temperature co-fired ceramic packages for microwave and millimeter wave gallium arsenide integrated circuits without antennas have also been developed as described in Polinski U.S. Pat. No. 4,899,118 and the references cited therein. In accordance with this procedure, an already fired substrate is provided for structural integrity and circuits are then built thereon in stacked layers in a low temperature co-fired format (about 800.degree. to 1000.degree. C.), each layer starting with low temperature "green" state materials that may have shrinkage and which is then processed in the "green" state (screen printing, via formation, etc.) with all layers then being fired together. Antennas or other radiating elements are not part of the system because sufficiently high structural integrity cannot be maintained in three dimensions with low temperature co-fired ceramic packages. Therefore, any antennas required are provided external to the package described in the patent.
A problem with low temperature co-fired packaging is that the materials used in low temperature co-firing have inferior microwave properties (higher loss tangent, lower reliability) than the materials that can be used in high temperature co-firing. Furthermore, low temperature co-firing techniques provide structures having inferior structural integrity than do equivalent structures fabricated using high temperature co-firing techniques themselves. The desire is to fabricate a total phased array package in a single material system and as a single package which includes therein integration of RF, digital, analog and antenna elements as well as other possible functions, such as I/O, which has superior microwave properties, improves reliability due to process step reductions and significantly reduces cost of manufacture.